In This Issue

正封面:刘中民等报道了Zn离子改性SAPO-18分子筛有效增加甲醇制烯烃(MTO)反应乙烯选择性和乙烯/丙烯比,将SAPO-18分子筛中以丙烯为主的产物分布调变为乙烯与丙烯选择性相近的产物分布.见本期第477–485页.     

碱金属碳酸盐改性对Au/TS-1催化剂的丙烯气相环氧化活性和稳定性的提升作用研究

制备了不同碱金属碳酸盐（Na₂CO₃、K₂CO₃、Rb₂CO₃和Cs₂CO₃）超声浸渍改性的Au/TS-1催化剂，采用XRD、ICP、XPS、UV-vis、NH₃-TPD、FT-IR和HAADF-STEM等手段对催化剂结构性质进行了表征，研究了碱金属碳酸盐改性对Au/TS-1催化剂的丙烯气相环氧化活性和稳定性的影响。结果表明，碱金属碳酸盐改性可以降低Au/TS-1催化剂的表面酸性，减缓环氧丙烷（PO）在催化剂表面吸附引起的积炭失活，抑制金颗粒粒径的增大；此外，Cs₂CO₃和Rb₂CO₃改性还可减少Au/TS-1催化剂上的骨架外Ti含量。碱金属碳酸盐改性后的Au/TS-1的催化活性和稳定性都得到明显的改善，其中，Cs₂CO₃改性的Au/TS-1表现出最佳的催化活性，丙烯转化率为6.2%，环氧丙烷选择性为86.2%，氢气利用效率为26.2%。相关研究为提高Au/TS-1催化剂的丙烯气相环氧化活性和稳定性提供了新的思路。     

在改性ZSM-5沸石上从甲醇合成低碳烯烃

沸石的改性可以扩大沸石的用途及提高目的产物的选择性.我们采用经过P,Mg,La,Th,Mn,W,Pd,Zn等改性的ZSM-5沸石,提高了从甲醇含成低碳烯烃的收率和乙烯的选择性.在磷改性的ZSM-5催化剂上,乙烯的选择性达45％(重),C_2—C_4收率为89％(重);在MgHZSM-5催化剂上,丙烯选择性达61％(重),C_2—C_4为95％(重).本文介绍了一种新改质剂—Al,及其Al_2O_3—ZSM-5催化剂的反应性能.     

镁改性对HZSM-5分子筛催化乙烯制丙烯的影响

采用等体积浸渍法制备了一系列不同Mg含量(0–1.0%)的HZSM-5分子筛。利用X射线衍射(XRD)、N_2吸附/脱附、铝魔角旋转固体核磁共振(~(27)AlMASNMR)、~(29)SiMASNMR、氨-程序升温脱附(NH_3-TPD)和吡啶吸附傅里叶变换红外(Pyridine-IR)光谱等技术对改性前后样品的结构和酸性进行了详细表征,在常压连续流动固定床反应器上考察其对乙烯转化制丙烯(ETP)反应的催化性能,评价了反应条件和Mg改性的影响。结果表明,在温度为550°C、乙烯体积空速GHSV=3000 h~(-1)的适宜反应条件下,0.5%适量镁改性HZSM-5导致乙烯转化率有所下降,但丙烯选择性增加到45%以上,而副产物芳烃的选择性降到8%以下。反应前样品的酸性表征和反应后积碳样品的TPO及~(13)CCP/MASNMR谱图分析表明适量镁改性使HZSM-5分子筛的总酸量和强B酸量减少而中强酸量增加,从而提高了丙烯的选择性,但是过量的镁改性使分子筛的总酸量明显减少,导致催化剂的活性显著下降。     

碱土金属氧化物担载Fe—MnO催化剂的CO加氢反应制低碳烯烃性能

碱土金属氧化物担载Ｆｅ－ＭｎＯ催化剂可大幅度提高低碳烯烃的选择性和ＣＯ转化率，添加碱金属助剂将进一步改善其催化性能；ＭｎＯ是铁催化剂由合成气制烯烃的有效助剂；碱土金属氧化物担体能抑制乙烯发生歧化反应及丙烯加氢反应，而ＭｎＯ助剂主要抑制乙烯加氢反应，从而有利于提高合成气制低碳烯烃的选择性。     

甲苯气相选择氧化制苯甲醛 Ⅳ.助剂锂、钾、铯对V_2O_5/TiO_2催化剂性能的影响

在Ｖ２Ｏ５／ＴｉＯ２催化剂中分别添加Ｌｉ、Ｋ、Ｃｓ等碱金属离子，利用ＢＥＴ、ＸＲＤ、ＸＰＳ、Ｈ２－ＴＰＲ、Ｏ２－ＴＰＤ－ＭＳ和化学分析方法，研究了催化剂结构和性能的变化．结果表明，催化剂在添加不同碱金属离子后，其结构和表面活性氧发生了很大变化．Ｋ离子可以改善催化剂的活性、提高反应选择性；Ｌｉ离子能提高催化剂活性，但在相当宽的温度范围内使反应选择性下降；在６９３Ｋ以下，Ｃｓ离子对催化剂的活性和选择性均起抑制作用．     

三种不同拓扑结构的分子筛在甲醇制烯烃反应中的性能对比

采用XRD、SEM、N₂吸附-脱附、NH₃-TPD研究了3种不同拓扑结构的分子筛SAPO-34、Al-ITQ-13和ZSM-5分子筛的孔结构、酸性分布对其甲醇制低碳烯烃中反应性能的影响.结果表明,SAPO-34对乙烯具有最好选择性,可达52.3%;ZSM-5和Al-ITQ-13则对丙烯具有良好的选择性可达50.3%和50.0%,丙烯选择性相当,但兼顾乙烯时,Al-ITQ-13较ZSM-5高,可达18.4%.3种分子筛反应性能的差异主要是其拓扑结构的不同引起的.孔道结构越小则越有利于小分子产物的生成,具有八元环结构的SAPO-34分子筛对小分子乙烯具有最高的选择性,而同时具有九元环和十元环结构的Al-ITQ-13由于孔道中含有一套九元环结构,使其与ZSM-5分子筛相比,在丙烯选择性相当的情况下,小分子产物乙烯明显增加.     

纳米HZSM-5沸石酸度的调节及对液化气裂解反应的影响

通过对纳米HZSM-5沸石进行钠离子浸渍改性和在小型常压固定床反应器中开展碳四液化气催化裂解制丙烯反应研究,探讨了催化剂酸度对反应选择性的影响.结果表明,钠离子改性能够选择性地去除纳米HZSM-5沸石表面的强酸中心,而对弱酸中心则基本无影响.在用钠离子改性基本上消除催化剂强酸中心的情况下,混合碳四液化气的催化裂解反应主要发生在丁烯分子上,丙烯的最高选择性可达60%,丙烯和乙烯的总选择性可达80%.     

改性Y分子筛的酸碱性能及吸附性能的研究

吡啶、吡咯、苯、甲苯、乙苯作为探针分子，在Li＋, Na＋, K＋, Cs＋改性的Y型分子筛上进行吸附，用TPD及IR方法系统地研究了不同碱金属离子改性的Y型分子筛的酸碱性能和吸附性能的变化. 结果表明，按Li、Na、K、Cs的顺序, 随着碱金属离子半径的增大, 其L酸酸强度依次减弱，L碱的强度逐渐增强.由于改性Y型分子筛所含碱金属离子的不同，其对芳烃的吸附的强弱及吸附量的大小亦不同.随着骨架外的阳离子的半径逐渐增大，碱的强度逐渐增强，与芳烃的作用愈强烈，导致TPD脱附峰温增高及芳烃和侧链上的C－H伸缩振动谱带向低波数位移愈多.由于位阻的原因，对含同一种碱金属离子的分子筛来说，随着芳烃侧链C数的增加，芳烃的吸附量逐渐减小.     

甲苯气相选择氧化制苯甲醛

在Ｖ２Ｏ５／ＴｉＯ２催化剂中分别添加Ｌｉ、Ｋ、Ｃｓ等碱金属离子，利用ＢＥＴ、ＸＲＤ、ＸＰＳ、Ｈ２ＴＰＲ、Ｏ２－ＴＰＤ－ＭＳ和化学分析方法，研究了催化剂结构和性能的变化。结果表明，催化剂在添加不同碱金属离子 后，其结构表面活性氧发生了很大变化，Ｋ离子可以改善催化剂的活性、提高反应选择性；Ｌｉ离子能提高催化剂活性，但在相当宽的温度范围内使反应选择性下降；在６９３Ｋ以下，Ｃｓ离子对催化剂的活性和选择性均     

金属离子负载修饰阳离子树脂在酯化反应中的研究

将催化精馏中常用作催化填料的强酸性阳离子交换树脂用金属离子负载修饰后，考察了树脂催化性能的改变及树脂结构对催化性能的影响。实验表明，经修饰后树脂的催化能力都高于原树脂，在不分水的情况下，合成乙酸乙酯时乙酸的转化率最高可达73％，具有很好的选择性，金属离子能与树脂的磺酸基团产生络合，提高了树指的催化性能，所形成的新酸中心不会被阳离子交换而失活。     

Potentialities and prospects for the use of alkaline phosphatases for determining metal ions

The published data on the nature, strength, and mechanism of metal ion effect on the catalytic activity of alkaline phosphatases and their apoenzymes of different origins are systematized and discussed. Procedures for determining metal ions are described. These procedures are based on the activating, inhibitory, and reactivating effects of metal ions on enzymes and apoenzymes. The approaches to the intentional improvement of the sensitivity and selectivity of determining metal ions are considered. Prospects are outlined for using alkaline phosphatases isolated from different sources in chemical analysis for determining metal ions in different samples.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 3, 2005, pp. 247–263.Original Russian Text Copyright © 2005 by Muginova, Zhavoronkova, Shekhovtsova.     

Ion exchange properties of monolithic and particle type iminodiacetic acid modified silica

A 10 cm silica monolith has been modified with iminodiacetic acid (IDA) groups and characterised for its selectivity toward alkali, alkaline earth, and selected transition metal cations. Physical characterisation of the modified monolith found non-homogeneous modification along the length of the monolith, although sufficient capacity was achieved to facilitate significant retention of alkaline earth and transition/heavy metal ions over a range of eluent pH and ionic strength conditions. For alkaline earth and transition/heavy metal ions, selectivity of the 10 cm IDA monolith closely matched that seen with a 25 cm IDA modified silica gel particle packed column, although the separation of alkali metal ions was noticeably poorer on the monolithic column. Peak efficiencies for most metal ions were of a similar order for both column types, except for Zn(II), which showed significant peak broadening on the IDA monolithic column.     

Salt-Bridge Supported Bilayer Lipid Membrane Modified with Calix[n]arenes as Alkali Cation Sensors

ABSTRACT

Potentiometric behaviors of a salt-bridge supported bilayer lipid membrane (Sb-BLM) modified with Calix[n]arene (n=4, 6, 8) derivatives are described for some alkali metal ions. The modified Sb-BLM was used as an alkali cation sensor. The membrane potentials were observed to generate Nernstian responses to the concentration of alkali metal ions in electrolyte. The Sb-BLM modified with the calix[n]arenes show high selectivity for individual alkali metal ions: Calix[8]arenes for K⁺, calix[6]arenes for Cs⁺ Calix[4]arenes show no selectivity for any alkali ions. The interacting mechanism is also discussed.     

Nickel- and cobalt-based heterogeneous catalytic systems for selective primary amination of alcohol with ammonia

It is one of the critical fields of green chemistry to catalyze the selective conversion of biomass-derived alcohol and ammonia to primary amines with extensive application. Recently, catalytic systems consisting of non-noble metal nickel- and cobalt-based catalysts have been developed for catalytic alcohol amination. This paper reviewed these two types of catalytic systems, which are classified as skeleton Co and Ni catalytic systems, supported and modified Co and Ni catalytic systems, emphasized on catalysts and catalysis, and clearly explained where zero-valent cobalt or nickel is active species for catalytic reaction. In supported catalysts, the catalytic active sites constituted by the catalytic active species and its micro-environment can regulate the efficiency of catalytic the reaction. While in modified catalysts, modifiers such as metal Fe, Re and Bi may modulate the catalytic active sites and change the catalytic selectivity. There are differences in structure and size between catalysts prepared by different methods, resulting in distinct interface and electronic properties for alcohol amination, which determines the structure–activity relationships of the catalytic system.     

Untersuchungen an oxidischen Katalysatoren. XXXVIII. Zum bifunktionellen Zusammenwirken metallischer und acider Zentren in Metall/HNaY-Zeolith-Katalysatoren

Studies on Oxide Catalysts. XXXVIII. On the Bifunctional Action of Metal Sites and Acid Sites in Metal/HNaY Zeolite Catalysts The catalytic activity and selectivity of HNaY zeolites containing nickel were investigated in the isomerization of n-hexane. In order to characterize independently the catalytic properties of the supported metal, the catalytic behaviour of these samples was determined in the dehydrogenation reaction of cyclohexane and in the hydrogenolysis of ethane. The catalytic properties of the metal in metal/HNaY zeolite catalysts are strongly modified by acid sites of the zeolite. This modification of the catalytic properties is attributed to electronic interactions between metal and zeolite.     

Preparation and Catalytic Properties of Amphiphilic Copolymer-Stabilized Platinum Metals Colloids

Several metal colloids stabilized by an amphiphilic copolymer, poly(1-vinylpyrrolidone-co-acrylic acid) (abbreviated as PVPAA), were prepared by refluxing alcohol-water mixed solutions of the corresponding metal precursors. They had small particle sizes and narrow size distributions. Their catalytic activity was tested by hydrogenation of cyclooctene, 1-dodecene, and ortho-chloronitrobenzene (o-CNB). With the introduction of nickel(II) ions to a PVPAA-stabilized platinum catalytic system, selective hydrogenation of o-CNB to ortho-chloroaniline (o-CAN) with 97.1% selectivity and 100% conversion was obtained. Copyright 2000 Academic Press.     

Target Self‐Enhanced Selectivity in Metal‐Specific DNAzymes

Highly selective recognition of metal ions by rational ligand design is challenging, and simple metal binding by biological ligands is often obscured by nonspecific interactions. In this work, binding‐triggered catalysis is used and metal selectivity is greatly increased by increasing the number of metal ions involved, as exemplified in a series of in vitro selected RNA‐cleaving DNAzymes. The cleavage junction is modified with a glycyl–histidine‐functionalized tertiary amine moiety to provide multiple potential metal coordination sites. DNAzymes that bind 1, 2, and 3 Zn²⁺ ions, increased their selectivity for Zn²⁺ over Co²⁺ ions from approximately 20‐, 1000‐, to 5000‐fold, respectively. This study offers important insights into metal recognition by combining rational ligand design and combinatorial selection, and it provides a set of new DNAzymes with excellent selectivity for Zn²⁺ ions.     

Smart nano-architectures as potential sensing tools for detecting heavy metal ions in aqueous matrices

The discharge of heavy metal ions into water resources as a result of human activities has become a global issue. Contamination with heavy metal ions poses a major threat to the environment and human health. Therefore, there is a dire need to probe the presence of heavy metal ions in a more selective, facile, quick, cost-effective and sensitive way. Conventional sensors are being utilized to sense heavy metal ions; however, various challenges and limitations like interference, overlapping of oxidation potential, selectivity and sensitivity are associated with them that limit their in-field applicability. Hence, nanomaterial based chemical sensors have emerged as an alternative substitute and are extensively employed for the detection of heavy metal ions as a potent analytical tool. The incorporation of nanomaterials in sensors increases their sensitivity, selectivity, portability, on-site detection capability and device performance. Nanomaterial based electrodes exhibit enhanced performance because surface of electrode at nano-scale level offers high catalytic potential, large active surface area and high conductivity. Therefore, this review addresses the recent progress on chemical sensors based on different nanomaterials such as carbon nanotubes (CNTs), metal nanoparticles, graphene, carbon quantum dots and nanocomposites for sensing heavy metals ions using different sensing approaches. Furthermore, various types of optical sensors such as fluorescence, luminescence and colorimetry sensors have been presented in detail.     

Target Self-Enhanced Selectivity in Metal-Specific DNAzymes

Highly selective recognition of metal ions by rational ligand design is challenging, and simple metal binding by biological ligands is often obscured by nonspecific interactions. In this work, binding-triggered catalysis is used and metal selectivity is greatly increased by increasing the number of metal ions involved, as exemplified in a series of in vitro selected RNA-cleaving DNAzymes. The cleavage junction is modified with a glycyl–histidine-functionalized tertiary amine moiety to provide multiple potential metal coordination sites. DNAzymes that bind 1, 2, and 3 Zn²⁺ ions, increased their selectivity for Zn²⁺ over Co²⁺ ions from approximately 20-, 1000-, to 5000-fold, respectively. This study offers important insights into metal recognition by combining rational ligand design and combinatorial selection, and it provides a set of new DNAzymes with excellent selectivity for Zn²⁺ ions.